If I am following this correctly.......then from your example there is a pretty steep angle ! On an angle like that......I think what people are suggesting .....is that on a lower 3rd behind the shoulder shot......you may only get one lung ! I have made those shots and recovered deer but a lung and some arteries were both hit !

Typically the high shot with a low exit would be better in that situation.......taking out both lungs ! It is hard for some folks to shoot that high though (on a steep angle)......so I think everyone tries to say "aim for the exit" !!